Process for the production of aluminum-silicon alloys free from carbide



Patented Feb. 18, 1930 UNITED, STATES PATENT OFFICE rnoonss FORTHEPRODUCTION or anummumsriacon ALLOYS FREE Fnom'canmnr.

No Drawing. Application filed May a, 1926,'Seria1 No. 107,788, and inGermany May 12, 1925.

10 owing to this high iron content, these alloys cannot be employed inthe production of pure aluminum silicon alloys capable of being cast.

If however correspondingly pure i. e., almost iron-free initialmaterials are employed,

15 it is possible to produce by electro-thermic treatment, an aluminumsilicon alloy which is almost free of iron. Nevertheless it isimpossible to obtain in this manner an alloy which has the compositionof commercial.

aluminum alloys containing for example 8 or 13% silicon. At the highreduction temperatures of the oxides prevailing in the electric furnacecarbon is taken up and such large amounts of carbides are formed thatthe .alloy cannot be industrially employed as a casting alloy. Ifhowever the silicon content is increased up to 35% and over, by suitablyproportioning the ingredients of the furnace charge, the surprisingobservation .is made,

that the formation of carbide disappears practically completely. Itshould be remarked that even a comparatively small proportion of carbon,is detrimental for the manufacture as well as for the employment of thealloy for casting purposes. 7

The alloys rich in silicon must be alloyed with pure aluminum inaccordance with the purpose for which they are to be used. Neverthelessif the preliminary alloy contains for example 2 to 3% carbon, subsequentalloying is practically impossible. If however the preliminary alloycontains a smaller proportion, for example 1' to 2%, of carbon, thenpart of the alloy will proceed to alloy, but so much residue remainsinthe form of carbon containing dross, that the process becomesuneconomical.

The discovery that an alloy of aluminum containing more than 35% siliconhardly 5 takes up any carbon is the more surprising,

as it is well known that both pure aluminum as well as pure silicon,form corresponding carbides with carbon at 1400 C.

The preliminary alloy produced according -to the present process can bealloyed with pure aluminum, and thereupon worked up to the knownaluminum silicon alloys, the usual known additions being also employedif desired. It is immaterial whether these sub stances such asforexample, small amounts of copper, are addedduring the formation of thesubsequent alloy or are already present in the preliminary alloyproduced by electrothermic means.

What I mean by the expression practically iron-free in the appendedclaims is an alloy whose iron content does not exceed 2%, preferably analloy containing less than 1% of iron. 1

I claim:

1. In a process for the production of practically carbide-freealuminum-silicon alloys by electro-thermic means, the step which comprises the production of a practically ironfree preliminary alloycontaining upwards of 35% of. silicon. I

2. In a process for the production of practically carbide-freealuminum-silicon alloys by electro-thermic means the step which comrisesthe production of a practically ironree preliminary alloy containingbetween 35% to 47% silicon.

3. A process for the production of practically carbide-freealuminum-silicon alloys by electro-thermic means, which comprises theproduction of a practically iron-free preliminary alloy containingupwards of 35% of silicon and alloying said preliminary alloy with purealuminum.

' 4. A process for the production of practically carbide-freealuminum-silicon alloys by electro-thermic means, which comprises theproduction of a practically iron-free preliminary alloycontainingupwards of 35% of silicon, alloying said preliminary alloy in admixturewith other known metals, to aluminum.

5. In a process for the production of practically carbide-free aluminumalloys by electrothermic means the-step which comprises electricallyheating to alloying temperature in the presence of reducing agentspractically iron-free aluminum compounds with practically iron-freesilicon compounds in such proportions that the resulting practicallyiron-free aluminum alloys contain not less than 35% of silicon.

6. In a rocess for the production of practically car ide-free aluminumalloys by electro-thermic means the step which comprises heating toalloying temperature in an electric furnace and in the presence ofreducing agents practically iron-free aluminum compounds withpractically iron-free silicon compounds in such proportions that theresulting practically iron-free aluminum alloys contain not less than35% of silicon.

In testimon whereof I aflix my signature.

CO AY VON GIRSEWALD

